The present invention disclosed herein relates to an optical apparatus and, more particularly, to an optical modulator modulating optical signals and an optical module including the same.
Recently, optical communication techniques on the basis of the IT technologies are rapidly evolved. The optical communication techniques may be largely divided into transmission, reception and modulation fields. Among them, the modulation field may have close relationship with high frequency characteristics and processing speed of optical signals. A typical optical modulator may include a Mach-Zehnder modulator and a thermo-optic modulator.
The Mach-Zehnder may include an input waveguide, an output waveguide, and a plurality of branch waveguides between the input and output waveguides. The branch waveguides may be branched into both sides from a rear end of the input waveguide. An optical signal from the input waveguide may be divided into optical signals having half intensity at the branch waveguides. The branch waveguides may include a ridge type silicon waveguide. Any one of the branch waveguides may have a refractive index adjusted by an external signal. Any one of the branch waveguides may retard a phase of the optical signal of half intensity or transfer the optical signal without phase retardation. The other branch waveguide may transfer the optical signal of half intensity without phase retardation. The branch waveguides may be connected at a front end of the output waveguide. The half intensity optical signals may be modulated by constructive interference or destructive interference between the branch waveguides and the output waveguide. When refractive indexes of the branch waveguides are the same, an optical signal input to the input waveguide may be output from the output waveguide without change. The optical signal may include data corresponding to value 1. On the contrary, the refractive indexes of the branch waveguides are different from each other, the half intensity optical signals may be destructed and output from the output waveguide. The output optical signal may include data corresponding to value 0. Accordingly, the output waveguide may output a modulated optical signal. However, the Mach-Zehnder modulator has a complex structure including the input waveguide, the branch waveguides, and the output waveguide.
The thermo-optic modulator may include a multi-mode optical fiber and a heater on the multi-mode optical fiber. Single-mode optical fibers may be connected to both ends of the multi-mode optical fiber. The signal mode and multi-mode optical fibers may be extended in one direction. The heater may be disposed in a crossing direction with the multi-mode optical fiber. The multi-mode optical fiber may have a refractive index changing along with heating by the heater. An optical signal may be modulated according to the refractive index of the multi-mode optical fiber. The multi-mode optical fiber may be manufactured in an emboss structure having a 3-dimensional size. However, the emboss structured multi-mode optical fiber may be manufactured with expensive etching equipment in a high-cost semiconductor process. Thus, a typical thermo-optic modulator has low productivity.